Compact Fluorescent Light Bulbs (CFLs)

CFL FAQs

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• What is a CFL?

  CFL stands for Compact Fluorescent Light bulb. CFLs use 75% percent less energy than incandescent bulbs, last up to 10 times longer, and can be used in ordinary light sockets.

• Why should I use CFLs?

  The real cost of a light bulb is not what it costs to purchase, but what it costs to use. CFLs use less energy than traditional incandescent bulbs. Even though a single CFL costs more than a single incandescent bulb, you'll actually save more money in the long run. Just one CFL can save you about $42 or more in energy cost over the life of each bulb. And if you switch out the six most-used incandescent light bulbs in your home for CFLs, you could save up to $250 over the lifetime of the bulbs. So the extra money you spend at the store is made up in savings on your energy bill. And since a single CFL lasts up to 10 times longer than an incandescent bulb, you'll save yourself some trips up the stepladder, too.

• Where should I use CFLs?

  Consider switching all your light bulbs to CFLs. Good locations to switch from incandescent light bulbs to CFLs include fixtures in your living room, family room, kitchen, bedroom and den. Outdoor light fixtures are also great places to use CFLs, just make sure you look for a CFL that says it's outdoor rated on the package if it's going to be directly exposed to the elements.

• How do CFLs work?

  CFLs create light differently than everyday incandescent bulbs. To produce the light we see, regular light bulbs use a filament that is heated by electricity and becomes white hot. CFLs, on the other hand, use a gas that creates invisible ultraviolet (UV) light when electricity goes through it. The UV light then hits a special coating inside the bulb, which converts it into visible light. Because CFLs create less heat to provide light, they are much more energy-efficient.

• Will CFLs fit in my existing light fixtures?

  CFLs can replace regular incandescent bulbs in almost any fixture. They come in a wide variety of sizes and shapes, including globe CFLs for your bathroom vanity, chandelier bulbs, CFLs for recessed down lights and, even ones shaped like traditional light bulbs.

  Check the packaging of the CFL to ensure that it may be used in an entirely enclosed fixture. Additionally, some ENERGY STAR^® qualified CFLs are specifically designed to provide dimming and three-way functionality—these options will be identified on the products' packaging.

• Can I use a CFL in a light fixture with a dimmer switch?

  You can use a CFL in a fixture that uses a dimmer switch, but make sure you look for a CFL that is made to be dimmable.  Check the package to make sure your new CFL is designed to be used with a dimmer switch.

• Can I use a CFL in my three-way lamp?

  Yes. As with incandescent bulbs, you need a three-way CFL to fully use all positions of your three-way lamp. A regular CFL will work in a three-way lamp in the middle or medium setting, and will not damage the bulb or shorten its life.

• Can I use a CFL in a recessed light fixture?

  Yes, but it is better to use a CFL labeled as a reflector instead of a spiral CFL because a reflector spreads light out wider and more evenly. Make sure any CFL you use has been approved for use in a recessed light fixture.

• Can I use a CFL in an enclosed light fixture?

  Not all CFLs are appropriate for enclosed fixtures; make sure the ones you choose are also labeled "suitable for use in enclosed fixtures."

• Can I use CFLs in the bathroom?

  CFLs will work in your bathroom, but the humidity could shorten a bulb's life. Run your ventilation fan during showers and baths and for 15 minutes afterwards.

• Will CFLs work in ceiling fans?

  Ceiling fans can be a great place to use CFLs. As with any light fixture, check the size of the bulbs needed to make sure the bulbs will fit in your ceiling fan fixture.

• Do CFLs work outside?

  CFLs are great outdoors, especially on the fixtures you leave on all night in your porch or lamp post. They are often the first place people try them out. Many CFLs can be used in covered or open fixtures outside, as well as in recessed cans and track lighting.

  In extreme cold, CFLs can take longer to reach their full brightness. CFLs are still a great way to light outdoors throughout the year.

• Don't CFLs have the distracting habit of humming and flickering?

  Most new fluorescent bulbs give you steady, hum-free light. The new electronic ballasts are not only more efficient, but also quiet and quick to start. Look for a quality product with the ENERGY STAR^® label and be sure to ask for a demonstration at your lighting or hardware store.

• Can I use CFLs in places where I turn the lights on / off a lot?

  CFLs work best when they are on for over 15 minutes at a time. To take full advantage of the energy savings and long life of ENERGY STAR^® qualified CFLs, it is best to use them in light fixtures you use more often.

• Do CFLs contain mercury? If so, how much?

  CFLs have a very small amount of mercury inside them— less than 5 milligrams. The amount of mercury in a CFL is 1/5 the amount in a watch battery. Mercury is commonly found in thermometers, light switches, thermostats, and batteries. Older household thermometers contain about 500 mg of mercury. It would take over 100 CFLs to equal that amount. No mercury is released when a CFL is used normally and isn't broken.

• What special precautions should I take with CFLs?

  Like anything made of glass, CFLs can break if you drop them, so be careful when you're handling them. Always screw and unscrew the bulb at its base, and never force a CFL into a light socket.

• What do I do if a CFL breaks?

  Read our step by step guide to CFL recycling and what to do if a CFL breaks.

• How do I dispose of CFLs? Do they need to be recycled?

  CFLs do need to be disposed of properly, and there are many retailers and municipal solid waste collection sites across the state where you can recycle your CFLs for free. Please visit our disposal locator or the www.mercvt.org website to find a disposal site near you. Vermont law states that all mercury labeled products must be disposed of with hazardous waste rather than included in your regular trash. CFLs contain a trace amount of mercury—less than 5 milligrams. The amount of mercury in a CFL is 1/5 the amount in a watch battery. Mercury is commonly found in thermometers, light switches, thermostats, and batteries. Older household thermometers contain about 500 mg of mercury. It would take over 100 CFLs to equal that amount.